The CTR is the key and most important factor to consider when assessing the relationship between the ads and keywords. In this way we find that keywords are working. Beware! a generic word could cause many impressions but few clicks on our ads will be printed in searches on google too broad and not relevant for our campaign.

A good first-CTR for a campaign should be, for example, about 3.50%.

The role of the budget is also key to improving our campaign and the statistics of it. Contrary to the general idea, invest a little at first and increase investment later (on visible results). With Google Adwords, the investment effort should occur at the beginning, and then maintained or reduced depending on individual cases and results.
We should try to budget Adwords campaign as if it were a gas vehicle.

The ideal is to reach more and better sites with the same fuel consumption, optimizing keywords and ads of the campaign, not adding more budget and burned again and again in the same impressions of little value. Again the main indicator of our improvements will be the CTR.